Figure 4 below shows a uniform metallic wire AB which is 1m long. It has a resistance of . It is…

Figure 4 below shows a uniform metallic wire AB which is 1m long. It has a resistance of $15\Omega$. It is connected in series with a resistor R of resistance $10\Omega$ and a battery $E_{1}$ which has an emf of 6V and internal resistance of $2\Omega$. Calculate the balancing length for the cell $E_{2}$ of emf 1.5V.